There continues to be a proliferation of wireless communications networks. For example, the FCC has proposed to allow unlicensed radio transmitters to operate within the broadcast television spectrum at locations where one or more of the allocated terrestrial television channels are not being used, so long as such unlicensed transmitters include safeguards that insure no interference with the reception of licensed terrestrial television signals. Various organizations developed ultrawideband (UWB) wireless communication technologies to take advantage of permitted unlicensed wireless device operations in licensed frequency bands.
In particular, the WIMEDIA® Alliance has developed specifications for wireless networks based upon UWB technology. For example, the WIMEDIA® MAC specification provides a fully distributed medium access control (MAC) protocol to support high-speed single-hop transmission between devices that are located in the vicinity of each other, e.g., so-called personal area networks (PANs). Meanwhile, in December 2005, the European Computer Manufacturer's Association (ECMA) published ECMA-368: “High Rate Ultra Wideband PHY and MAC Standard” specifying an ultra wideband physical layer (PHY) and distributed MAC sublayer for a high-speed, short range, distributed access wireless network that may include portable and fixed devices.
As used herein, a device in a wireless network may also be referred to as a terminal or a node. Also as used herein, a wireless network is said to have “distributed access” when there is no central controller, base station, master station, etc. that governs or controls access to the communication resources (e.g., time slots in a reservation-based data transfer protocol) of the wireless network by the other devices in the network.
However, due to the regulatory restriction on transmission power, the transmission range of devices using the current WIMEDIA® MAC is limited, and decreases with any increase of the physical transmission rate. Accordingly, due to transmission range limitations, in some cases it is not possible for one device in a wireless personal area network (PAN) to transmit data to another device in the same network if the two devices are physically separated by too great of a distance. In other cases, where the two devices may be closer together, transmission may be possible, but only at reduced data rates. However, there are a number of applications where it would be highly desirable for devices that are remotely located from each other by a significant distance to be able to send and receive data to and from each other at higher data rates than are supported by the transmission power limitations on the devices.
Accordingly, it would be desirable to provide a method of transmitting data from one device to another device in a distributed wireless network even if the two devices are physically separated by too great of a distance for direct wireless transmission. It would also be desirable to provide such a method that supports high data transmission rates and spectrum efficiency. It would further be desirable to provide a method of reserving resources for multi-hop transmission from device to device in a distributed access wireless communications network.
In one aspect of the invention, in a communication network comprising a plurality of devices communicating using a reservation-based data transfer protocol having a superframe comprising a plurality of slots, a method of reserving X slots for transmitting data from a source device to a destination device via multi-hop relay is provided. The method includes sending a first hop reservation request from the source device, addressed to a second device different from the destination device, for transmitting data from the source device to the destination device. The first hop reservation request identifies the source device, the destination device, and X proposed slots to be reserved for a first hop between the source device and the second device. The method also includes, at the source device, receiving a first message, addressed to the source device from the second device, indicating that the first hop reservation request is pending and that the X slots proposed by the source device have been reserved by the second device. The method further includes, at the source device, receiving a subsequent message, addressed to the source device from the second device, indicating that a final hop reservation request has been accepted by the destination device, corresponding to the first hop reservation request of the source device.
In another aspect of the invention, in a communication network comprising a plurality of devices communicating using a reservation-based data transfer protocol having a superframe comprising a plurality of slots, a method of reserving slots for transmitting data from a source device to a destination device via multi-hop relay is provided. The method includes receiving at an Nth device an (N−1)th hop reservation request for transmitting data from a source device to a destination device via multi-hop relay. The reservation request identifies the source device, the destination device, and X proposed slots to be reserved for an (N−1)th hop between an (N−1)th device and the Nth device. The method includes, when the X proposed slots to be reserved for the (N−1)th hop are available at the Nth device: transmitting a message from the Nth device, addressed to the (N−1)th device, indicating that the reservation request is pending and that the X slots proposed by the (N−1)th device have been reserved by the Nth device; and sending an Nth hop reservation request from the Nth device, addressed to an (N+1)th device, for transmitting the data from the source device to the destination device, the Nth hop reservation request identifying the source device, the destination device, and X proposed slots to be reserved for an Nth hop between the Nth device and the (N+1)th device, wherein the X slots proposed by the Nth device to be reserved for the Nth hop are different from the X slots proposed by an (N−1)th device to be reserved for the (N−1)th hop. The method also includes, when the X proposed slots to be reserved for the (N−1)th hop are not available at the Nth device, transmitting a message from the Nth device, addressed to the (N−1)th device, indicating that the reservation request is denied.